FAQ : Debunking the 4G64 Myth

FAQ : Debunking the 4G64 Myth


For those of us that have heard 4G64 Myths in the Yahoo groups for quite some time, have heard these questions over and over again. Thus, the creation of this FAQ (Frequently Asked Questions) listing. Thank you for taking the time to look over it and spare us many extra hours of typing to answer your question.

This FAQ is primarily for the 94-98 Galant and 95-99 Eclipse Spyder, but other varients of the 4G64 engine do exist, and may enter into the discussion (such as the G64B and G4CS engines).

The difference between the 4G63 and the slightly larger non turbo 4G64 is a slightly larger bore ( the 4G63T at 85mm vs the 4G64 86.5mm) and a longer stroke ( 88mm for the 4G63 vs 100mm for thr 4G64. The deck of the 4G64 is also 6mm higher than the turbo counterpart, which is the major difference in the shortblock.

This longer stroke provides the grunt down low but also means that the motor is less balanced at higher RPMs, a fact that doesn’t deter most enthusiasts as all they intend to do is slap on a huge turbo.

1) Can the 4G64 be turbocharged?
Yes, it can. There is a full procedure on how to do it listed on this website. However, special caution needs to be exercised. This is not something you should be doing if you are not very familiar with working on cars, or unfamiliar with the perils of turbocharging a car that was never meant to be forced induction.

2) Can you put the DOHC head from a turbo 4G63 onto the 4G64?
Yes, it can be done, and has been done. Mitsubishi made this entirely possible and easy when it released the 1994 Galant GS, which came stock with the 4G64 DOHC engine. You can use the stock bottom end, and bolt on a DOHC head, using some parts from the above mentioned 94 Galant, such as the timing belt and cam gears (or adjustable 4G63t cam gears).



2a) What are the main differences/advantages in the DOHC head vs. SOHC head?
While the exhaust ports are the same size on all of the heads in question (1g and 2g DOHC and 4G64 SOHC), the intake ports vary wildly between them. The largest intake ports are found on the 1G DOHC head, followed by the 2G DOHC head, and finally our 4G64 SOHC head. For comparison, the 2G DOHC head intake port is 27mm x 55mm in size, while our 4G64 SOHC intake port is 27mm x 43.5mm in size. That’s about a 20% reduction in size. For NA applications, the extra size won’t gain you a ton, but in turbo applications, the better flow will be very noticable.

3) What are the differences between the Spyder 4G64 and the Galant 4G64?
There are several differences. Most noteworthy is that the Galant has a distributor instead of a DIS. This will cause problems with installing the DOHC head on a Galant, unless you swap out the ECU and wiring to convert over. More info will be posted on this when it becomes known. There are other minor differences. The intake manifold doesn’t have a spot to mount the DIS module. The valve cover is missing a mounting point. Obviously, the air intake systems are somewhat different. In other words, cosmetic differences.

4) What performance mods can I do to my 4G64 engine?
There is a fairly complete listing for the Spyder that can be found HERE. Some of the Galant modifications will differ (exhaust, suspension, etc.)

5) What kind of power increase can I see from turbocharging my engine?
Running 8-9psi boost, you should see about a 100HP gain over a stock 4G64 engine. Of course, every custom setup is different, and as such, your gains will vary.

6) Where can I go to find out more information, and talk with people who have done these mods?
There are two main groups for these types of modifications. For strictly engine upgrades, the best spot is the 4G64 Yahoo Message Group.
For Galant specific questions & research, go to The Galant Center (TGC) forumns.

7) Can I convert my Spyder to an AWD? What is needed to do the AWD Conversion?
Can it be done? Pro Street’s very own Mitsubishi Eclipse Spyder was the first AWD conversion done.



The chassis/body of the Spyder is the same as the AWD Eclipse. Is it a very large and expensive project? Yes, it is. However, those of you that absolutely want it done, you first need a nearly complete Eclipse GSX donor car to get the parts from. Here is a list of parts that are needed:

AWD Tranny & Transfer Case
AWD Flywheel & AWD Flywheel backing plate
AWD Front axle Assy’s
Complete Driveshaft Assy including the bearings and nuts and bolts
Fuel tank assy with the complete filler neck assy
Rear Suspension Assy with all nuts and bolts
Complete exhaust system from an AWD (DP, Cat, Cat back exhaust)

8) What is ideal first suspension mod?
The cheapest suspension mod that will do the most good for the Spyder is a front tower strut tie bar. It costs under $100. In most cases under $50. It’s a basic metal bar that ties the front shock towers together. It tightens up the front end, and removes much of the cowl shake. This is what happens when you hit a pot hole and see the windshield wobble. Getting the towers tied removes this looseness.

8b) What’s the deal with the rear sway bar on the Spyder GS?
The Spyder GS did not come with a stock rear sway bar. One can be added, however, because the parts needed to do the conversion match with the Spyder GST. The sway bars I personally recommend can be found HERE.  The needed parts list (prices approx):

2 Rear Control Arms MR131754 $55.00/each
2 End Links MB892982 $15.00/each
2 Brackets MB515245 $ 7.00/each
4 Nuts MS440504 $ 1.00/each
4 Bolts MF241251 $ 1.00/each

9) What springs and shocks do I use on my Spyder GS?
Since the Spyder has considerable weight in the rear from all the body strengthening, you want to get springs designed for a AWD Eclipse. If you get springs from a FWD Eclipse, you will be sagging in the rear. However, struts (shocks) are the same as a FWD Eclipse. Replace the struts BEFORE or at the same time as your springs. The stiffer springs would wear out your stock struts very quickly.

10) Can I do a rear Drum Brake to Disc Brake conversion on my Spyder GS?
Yes. The procedure is fairly simple, and can be done for a reasonable amount of money. For more information, see my Drum to Disc Conversion Page.

11) What air intake do I use?
There is not a cold air intake pipe made for either the Spyder GS or the 7G Galant. However, both cars utilize the same Mass Airflow Sensor (MAS) as the 2G Eclipse turbo. As such, any hi-flow filter kit (such as the K&N FIPK or similar) that you can buy for the Eclipse turbo will bolt up to the 4G64 intake. While this is not completely optimum (because of sucking in higher temp
ure engine compartment air), it does add a good 5-10HP, and allows better airflow at higher RPM’s.

BEWARE:  Many companies are falsely advertising cold air intake kits for the Spyder GS. At this time, there is NO KNOWN kit that fits the Spyder GS. These companies are lying. They are too stupid to know the difference between the 420a and 4G64 engines. Even when confronted with the truth, they ignore all reason, and will not retract their ads. The simple way to know is if there is a place for the MAS. If there isn’t, then it doesn’t work, this is one of the biggest and most false 4G64 Myth.

12) What differences are there in the ’96 Spyder vs. 97-99 Spyder?
Besides the obvious changes that happened to the front and rear body panels of all Eclipse models, there are several other differences. First off, if you plan on putting a turbo on your 1996 Spyder, you’ll find that the washer fluid bottle is right where the stock SMIC would go, instead of in the back of the car. The 97-99 models also have a fuel pump module which varies voltage to the pump based on engine RPM. The 1996 car does not have this. There are also the cosmetic differences, such as black door handles & mirrors, instead of having them painted the body color. The 1996 Spyder also has a stationary black antenna instead of a power antenna.

13) How do I wire the resistor pack in if I install larger low impedance injectors (such as stock 450cc turbo injectors)?
The injectors get fed a constant 12v signal. The ECU turns on and off the ground to make the injectors pulse. As such, cut the 12v power lead to each injector, with room to splice a wire back to it. Run all 4 power wires to the center main wire on the resistor pack. Then, spice a wire from each of the 4 cut injector leads to one of the 4 remaining leads on the resistor pack. That’s it!

14) What about all the “power adders” I see on Ebay and elsewhere?
Buying any power adders from eBay for the Spyder GS falls into two categories of caution. 1) See the FAQ question on the Chrysler 420A motor. 2) Is the power adder a scam/snake oil item? Once you passed the item through the sanity check #1, be sure to check the category of item for evidence of snake oil using the Internet first. If the item is an electric supercharger, any sort of vortex/tornado item, or if it contains a “magnet” to improve performance, then most likely do not bother.

15) Does anyone make headers for my car? What if I want to go turbo?
Since the exhaust manifold gasket pattern is the same as the 4g63, one possible source for headers is 4g63 NT headers. Another source for headers is RPW in Australia. NT Headers can not be reused for turbocharging. Check out more information before believing this common 4G64 Myth.

16) Is the Chrysler 420A motor in the Eclipse GS and the Neon the same motor as the Eclipse Spyder GS?
The Chrysler 420A is absolutely NOT the same motor as the Eclipse Spyder GS. When purchasing any bolt on component for the 4g64, the first sanity check you must make is to ask to see if the part is compatible with the Eclipse GS. If it is, 9 times out of 10 it will not fit the Eclipse Spyder. The Chrysler 420A is completely unrelated to the Mitsubishi 2.4L engine.


Happy Swapping!



  1. Basically, not worth the time or money, just buy a car that already has those options installed from the factory. For what it is going to cost for all of these conversions, one could buy one outright. The only people that look into doing these things are kids, wishful dreamers with no real money.

    • Hi DRock99, thanks for reading.

      Although a 4G63 DOHC head can make a powerful stroker out of a 4G64, you are pretty much on point with your assessment.

      Best to just sell and move on to a turbocharged 4G63.

      Thanks for commenting!

  2. In response to #11. I own a 3g Spyder with a 4g64, Injen makes a CAI for my vehicle. It is also supposed to match with the early 2000 Galant. Thank you for this listing. Very informative!

  3. Thank you so much!

    I’ve read countless articles about some of these topics but none have been nearly as information as yours. I own a 1999 Eclipse Spyder GS and am having the hardest time finding a cat back system. Your article (especially the modifications list) clarified a lot.

    Thank you again.